5.7.606–5.7.649: Access denied, banned sending IP
Microsoft returns a code from 5.7.606 to 5.7.649 when the IP you send from is on its blocked senders list. Check that the IP is not compromised or sending bad traffic, then request removal through Microsoft’s self-service delist portal using the IP address from the bounce.
The exact message
Microsoft 365 / Exchange Online
5.7.606-649 Access denied, banned sending IP [IP1.IP2.IP3.IP4]
Why it happens
- The sending IP sent spam, whether from you, a compromised account, or a previous user of a shared or recycled IP.
- Sudden high volume from an IP with no history.
How to fix it
- Confirm the IP from the bounce and check it against public blocklists.
- Fix whatever produced the bad traffic.
- Submit the IP at Microsoft’s delist portal and follow the confirmation email.
If you send cold email
If you send through a shared SMTP relay, the IP may have been banned because of another customer. Mailbox-provider IPs (Google Workspace, Microsoft 365) are rarely the ones banned; self-hosted and relay IPs are.
How WarmHawk handles it
WarmHawk pauses a mailbox on its own once its hard-bounce rate passes 5% over at least 20 sends, and pauses a campaign at that campaign’s own bounce threshold, so a bad list stops before it drags the domain down. Every sending domain is re-checked against DNS blocklists hourly, and a mailbox only reaches campaign volume after at least 14 days of warmup with a 90% inbox rate. A mailbox whose inbox rate falls below 70% goes back to warmup. How WarmHawk works →
Check your domain now
These free checkers read your live DNS: no account, up to 15 domains at once.
Related bounce codes
- 5.7.511Access denied, banned sender (IP)
- 4.7.500Access denied, please try again later
- 5.7.513Your IP is on the recipient’s own block list
Sources, checked 2026-09-29: Microsoft Learn: NDRs and SMTP errors in Exchange Online · Microsoft Learn: Use the delist portal. Have a different bounce? Paste it into the decoder →
Questions
5.7.606 questions
What does 5.7.606 mean?+
Microsoft returns a code from 5.7.606 to 5.7.649 when the IP you send from is on its blocked senders list. Check that the IP is not compromised or sending bad traffic, then request removal through Microsoft’s self-service delist portal using the IP address from the bounce.
Is 5.7.606 a temporary or permanent error?+
Permanent. The message will not be retried, and sending it again unchanged will fail the same way until the cause is fixed.
How do I fix 5.7.606?+
Confirm the IP from the bounce and check it against public blocklists. Fix whatever produced the bad traffic. Submit the IP at Microsoft’s delist portal and follow the confirmation email.